title: Effects of hypoxia on contractility of isolated fetal lamb cerebral arteries.
abstract: We studied the contractile properties of isolated cerebral arteries in near term fetal lambs, as well as the magnitudes and rates of relaxation during moderate hypoxia. Paired 5-mm segments of basilar, middle cerebral, posterior communicating, and common carotid arteries were suspended in a temperature controlled bath and isometric tension measured during 122 mM K(+)-induced contractions. In one vessel of each pair hypoxia was imposed by switching the bubbling gas from 95% O2 + 5% CO2 to 95% N2 + 5% CO2 4 minutes into a K+ contraction, thus lowering the bath PO2 to approximately 15 Torr. After 15 min exposure to hypoxia the middle cerebral artery had relaxed 61%, the posterior communicating 46%, the basilar 44%, and the common carotid only 18% compared to normoxic controls. All cerebral arteries relaxed relatively rapidly (relaxation rates of 42-45 x 10(-4) s-1), whereas the common carotid relaxed slowly (20 x 10(-4) sec-1). The data indicate that these cerebral arteries play an important role in regulating blood flow responses during hypoxemia in intact fetuses.
authors.affiliation: Department of Physiology, School of Medicine, Loma Linda University, California.
authors.forename: R D
authors.initials: RD
authors.lastname: Gilbert
authors.forename: W J
authors.initials: WJ
authors.lastname: Pearce
authors.forename: S
authors.initials: S
authors.lastname: Ashwal
authors.forename: L D
authors.initials: LD
authors.lastname: Longo
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D002536:Cerebral Arteries / Q000196:embryology / Q000502:physiology*; D046508:Culture Techniques; D009119:Muscle Contraction; D009126:Muscle Relaxation; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010100:Oxygen / Q000502:physiology*; D012756:Sheep / Q000196:embryology* / Q000502:physiology
chemical_list: D010100:Oxygen